Various safety features have been used to protect people from electrical shock from electrical devices such as breaker boxes, other types of control boxes, and protective-battery systems. Safety features also exist to protect people from other hazardous conditions such as high heat, cold, or radiation levels.
A common safety feature for breaker boxes or control boxes is a mechanical locking mechanism that engages automatically whenever a main power switch is turned on.
Turning to the figures, and more particularly the first figures, FIG. 1 shows an example of a breaker box or control box 100, referred to generally herein as a power box. The power box 100 is used in an environment 102, such as an assembly plant or factory. The power box 100 has an input 103 for receiving a connection to a main power source 104, such as a power input cable.
The power box 100 shown in FIG. 1 includes a cover panel or door 106 or other access component or feature. Some power boxes 100 (not shown in FIG. 1) are open, lacking such a door. The box 100 can also include a conventional lock 108 releasable by a release switch 110. And the box 100 can have a power breaker or switch 112 controlling input of power to the box from the power source 104. In some cases, the lock and switch are connected indirectly so that throwing the switch 112 to turn the power on also results in the lock 108 locking.
Systems having such a switch 112, or other activating feature that can be selectively activated by a person, can be referred to as active-actuation systems, being configured to be actuated actively for actuating one or more safety mechanisms—e.g., locking mechanism, blocking mechanism, and mechanism to hold closed an electrical connection between the source and a load (e.g., alarm(s), resistor(s), etc.), thereby promoting drainage of unwanted electrical charge. The mechanism described primarily in connection with FIGS. 2-8, consists of the prior two mechanisms, the locking and blocking mechanisms.
When the main power to such boxes is turned off—e.g., the main power switch 112 is turned off (and a main lock can here be automatically released), residual power may still be in the system, such as by not having discharged from each sub-unit within the box, or by the system being mis-wired. In this event, personnel accessing the box may be exposed undesirably to the charge, believing that they are safe due to the box being unlocked/openable and/or the switch being turned off.
Some boxes have secondary power feeds, which can be mis-wired so the current therefrom reaches undesirably certain parts of the system 200 with which users could come into contact. An example secondary power feed is identified by reference numeral 105 in FIG. 1. As an example, the system 200 could include a separate alternating (AC) line, such as a 120-volt line (single-phase or three-phase, for instance) and, if a part of the system is mis-wired, its power could back feed into a main machine so that even though a main switch or breaker is switched off, and the mechanical lock released, power could still be supplied to the system. As another example, the system 200 could include a direct current (DC) line, such as in regards to capacitor power cabinets connected to DC motor drives.
Again, personnel accessing the box may be exposed undesirably to the charge, believing that they are safe due to the box opening.
Risk of shock is also present in connection with electrical devices having a local battery source. For instance, in the event of an emergency, charge stemming from the battery could theoretically extend to various parts external and proximate to it.
Regarding temperature and radiation, a common safety system is to use a chromo-sensitive material that changes its appearance when exposed to heat, cold, or radiation, thereby warning people of the condition. Other systems use gages, such as a thermometer or radiometer to warn people. One shortcoming of these methods is that they still allow the people, who may or may not notice the warning, to access the hazardous condition.
There is a need for systems and methods for protecting persons from electric charge and other unwanted conditions (e.g., heat, cold, radiation) in these and similar scenarios.